The proliferation of air bag systems in vehicles has and continues to be dramatic. In the recent past, for instance, air bags were only available on certain models of cars and were typically limited to being installed in the steering column. Now, air bags are standard equipment on almost all current models of cars and trucks. Further, in addition to driver-side air bags, vehicles now contain passenger-side air bags and side-curtain air bags that may be located along the side walls of a vehicle and can, for instance, extend substantially the entire length of an interior side of a passenger compartment.
When installed in a vehicle, air bags are typically folded and located in small compartments. The air bags are placed in communication with a gas inflation system that inflates the air bag when a collision between the vehicle and another object is detected.
Air bags are made from materials, such as woven fabrics, that must have a unique combination of properties. For instance, the air bags should be capable of being folded into small shapes and should also be able to withstand broad temperature swings without degrading. For example, the inside of a vehicle can become relatively warm in the summer and relatively cold in the winter.
Air bags should also be made from materials that are capable of withstanding the force of the inflation gas while, in some embodiments, also being capable of quickly deflating after being inflated in a process referred to as “leak down”. Air bag materials should also have relatively high tensile strength and tear strength and should be capable of being made with a relatively low permeability.
In the past, many air bags were made from a woven fabric containing multifilament yarns, such as yarns made from nylon. The air bag fabrics were made using various different weaving systems. For instance, in some applications, the fabrics were woven on a Rapier weaving machine.
Recently, various attempts have been made to produce air bag fabrics on water jet weaving machines. In a water jet loom, the weft or pick yarns are moved in the cross machine direction through a shed formed by the warp yarns using jet streams of water. Of particular advantage, water jet weaving machines are much faster and have a higher throughput than conventional Rapier weaving machines.
The use of water jet looms to produce air bag fabrics, for instance, is disclosed in U.S. Pat. Nos. 5,421,378; 5,503,197; 5,650,207; 6,413,452; and 6,796,337, which are all incorporated herein by reference. In the past, when producing air bag fabrics on water jet looms, it was generally taught not to apply a size to the warp yarns during the weaving process. Sizing is a procedure where the warp yarns are coated with a substance, such as a polymeric material that facilitates weaving, such as by reducing friction and/or improving abrasion resistance. The process of applying a size is commonly called “slashing”. Abrasion reduction contributes to a reduction in the number of breaks, strip backs, fuzz balls, etc. all of which translate into a higher percentage of off-quality and into more machine stops during the course of weaving.
In the past, a size was not typically applied to the warp yarns during a water jet weaving process for various reasons. For instance, water jet weaving processes can be less stressful on the yarns during weaving in comparison to other conventional weaving systems. This is possible in part because the water introduced in this process acts in limited capacity as a size by adding coherency and lubrication to the yarn. Consequently, a size was generally not necessary in order to prevent yarn breakage. Further, the use of a size requires several extra steps in the fabrication process. In addition, sizes can add cost to the product and typically were removed from the yarns after being applied in a process known as “scouring”.
The present disclosure is generally directed to further improvements in producing air bag fabrics on water jet weaving machines. In particular, the present disclosure is directed to the use of a size composition during water jet weaving in which the formed fabric does not necessarily have to undergo scouring to remove the size composition. Of particular advantage, the size composition not only improves the efficiency of the weaving process but can also provide benefits and advantages to the final product.